A needed spot in a team is not a passenger. Try do a HM flashpoint with only a healer and a tank, with standard gear.
I would never call a needed spot a passenger.
Now ontopic on my original subject please
That spot is needed to make the queue pop through GF. It's not needed to clear the instance. Half of the content in HM FPs has been soloed and the other half has been 2 manned.
Now I personally don't mind fighting bosses we would normally skip, I DO mind doing Bonus bosses in a HM FP. Each boss only take a short amount of time, but activating a bonus boss means a lot of trash has to be fought. That said, there are some bosses that I would rather skip anyway, especially if they are prone to wiping a group like the "run through" boss on HM BoI.
Now the key offenders for boss skipping are BoI and T5, each only requiring you to fight 1 boss and a handful of trash. Compare a 12 minute run to the end with a 30-45 minute full clear and tell me which you'd rather do, given that most people are only getting BH comms and those that could use the gear are still able to get it in other FPs from non-skippable bosses. For example, Kaon, Esseles, D7 and MP all have plenty of non-skippable bosses for you to fight. Enjoy a quick run when you can and we'll do a proper clear when I have to.